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Unformatted text preview: ATP is the most important form of potential energy stored in all cells – it stores energy in the ester bonds between its phosphate groups. When the energy of a system decreases, the energy of the rest of the universe increases- Similar to how entropy decreasing in one system is counteracted by an increase in entropy in another system.- Disorder (entropy) tends to increase Spontaneous reactions occur if it increases the disorder of the universe ΔG = ΔH – TΔS ΔH = ΔE – PΔV Notice that this is a variation of ΔE = q (ΔH) + w (PΔV)- Change in E is the bond energy of products or reactants in a system, P is the pressure, and V is the volume- In a cell, since cellular reactions take place in the liquid phase, H is approximately equal to E, since the change in volume is negligible . In the body, endergonic reactions (ones with a positive delta ‘G’) are driven by reaction coupling to exergonic reactions (ones that are spontaneous)- Distinguish from endothermic and exothermic If ΔG > 0, energy must be added to a system to make the reaction occur.- Distinguish between ΔG and ΔG▫’ (the latter is where you have pH of 7, and other standard conditions. This term also describes the intrinsic properties of the reactants and products) ΔG▫’ = -RT ln K’ eq ΔG = ΔG▫’ + RT ln K- K is the concentration of products over the concentration of reactants (at equilibrium) Spontaneous reactions may proceed without additional energy input- Implies nothing about the rate of a reaction ΔG doesn’t tell you anything about the pathway a reaction takes or the rate of reaction; it’s only a measurement of the difference in free energy between reactants and products. The more transition state intermediates that are formed, the greater the amount of product produced (i.e. the more rapid the rate of the reaction). This is done by lowering the activation energy required to reach those transition states. A catalyst lowers the activation energy of a reaction without changing the overall free energy change (ΔG)- It instead stabilizes the transition state- Catalysts are regenerated with each reaction cycle.- They affect the rate at which the reactants and products reach equilibrium- They do not alter reaction equilibria Reactions with ΔG > 0 can be coupled with reactions where...
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This note was uploaded on 11/07/2010 for the course CBN 356 taught by Professor Merill during the Spring '08 term at Rutgers.
- Spring '08